Abstract: By using two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DCA), this paper analyzed the environmental gradients of the species diversity and distribution of permafrost wetland plant communities in 12 valleys at different latitudes of the Great Xing’an Mountains. The plant communities in the 12 valleys could be classified into four plant associations, based on the latitudes. The classification results of TWINSPAN reflected well the relationships between the distribution of the plant associations and the latitudes, and these relationships were better validated by DCA ordination. The species diversity increased with decreasing latitude and increasing mean annual temperature, mean annual precipitation, mean temperature in January, and aridity. The dominant and co-dominant species in shrub and herb layers were mostly helophytes and hygrophytes. With decreasing latitude, the helophytes and hygrophytes decreased or disappeared, while mesophytes increased.

Key words: Great Xing’an Mountains, permafrost wetland, two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), species diversity